To Detach or Not to Detach: When Should You Use `std::thread::detach()`?

Understanding the Difference Between Calling and Not Calling std::thread::detach()

When utilizing std::thread to enhance application performance, it's crucial to understand the distinction between calling detach() and not.

What Happens When detach() is Not Called?

Without invoking detach(), the thread created operates independently within its own execution path. In this scenario:

void Someclass::Somefunction() {
    //...

    std::thread t([ ] {
        printf("thread called without detach");
    });

    //some code here
}

The main thread will execute "some code here" while the newly created thread prints "thread called without detach."

When to Call detach()

Calling detach() alters how the thread interacts with the main thread:

void Someclass::Somefunction() {
    //...

    std::thread t([ ] {
        printf("thread called with detach");
    });

    t.detach();

    //some code here
}

Now, the main thread will execute "some code here" immediately after the thread is launched. Importantly, detach() does not wait for the thread to complete.

Determining When to Use detach()

Based on the above differences, consider the following guidelines:

1. Use join() if you require the main thread to wait for the thread to finish before proceeding.

2. Use detach() only if:

   • You need flexibility and are willing to manually implement synchronization mechanisms to handle thread completion.
   • The thread's execution does not require any further interaction with the main thread after its launch.

Caution:

It's crucial to note that when a program terminates (i.e., main returns) with detached threads still running, their stack is not unwound, potentially leaving destructors unexecuted. This can lead to data corruption and other undesirable consequences.

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